How can I trace a connection through a proxy server and/or a VPN?

"The only way to trace something through a proxy/VPN is to gain access to the logs kept by that proxy, normally by contacting the owner, giving them a time and IP that was accessed (beware of time zones), and asking them to find out who was connected to you at that time. Some legitimate providers will help you with, for serious activity, most of the proxies/VPNs are on rooted machines, so no one will be keeping logs.

Most FTP servers will allow you to block someone after a number of failed login attempts, you might also be able to do the same from your firewall, depending on the configuration. The odds of you tracing this back to someone are almost zero, all you can do is check your machine hasn't been compromised, make sure your passwords are secure, and set up your server to block attackers."